On Mon 2021-06-07T20:14:00+0100 Clive D.W. Feather via tz hath writ:
I was wandering round the Fitzwilliam Museum in Cambridge the other day and noticed a Thomas Tompion (1639-1713) clock. It had two hands and a dial with Roman numerals I to XII twice going round it. Outside that, in Arabic numerals, were 5, 10, ..., 60, also twice. At the top it said "EQVAL 60 TIME".
So 1800 is perhaps a bit late, at least for some places.
A clock of this quality would be sold as a "regulator" and priced accordingly. Not even most observatories had clocks accurate to one second until around 1800. If one second is the standard then 1800 is a good guess at the year. -- Steve Allen <sla@ucolick.org> WGS-84 (GPS) UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m